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Geotextile Soil Reinforcement Supplemental Technical Specification for Geotextile Soil Reinforcement SCDOT Designation: SC-M-203-3 (01/18) 1.0 DESCRIPTION 1.1 The requirements of this specification consist of furnishing all necessary submittals and materials for providing geotextile soil reinforcement in accordance with the details shown on the plans and the requirements of this Supplement Technical Specification (STS, the project Specifications, Special Provisions or as directed by the Resident Construction Engineer (RCE). For geotextiles used for subgrade stabilization see STS Geosynthetic Materials for Separation and Stabilization (SC-M-203-1). 2.0 TESTING STANDARDS 2.1 Use the latest edition of the testing standards indicated in this specification. Substitution of standards will require the prior written approval of the Materials and Research Engineer (MRE) with concurrence of the Geotechnical Engineer-of-Record (GEOR). Provide copies of all substituted standards to the Resident Construction Engineer (RCE) if requested. The RCE will provide the copies to the MRE and GEOR for approval and concurrence. 3.0 MATERIAL 3.1 A geotextile is defined as permeable planar polymeric material used with foundation, soil, rock, earth, or any other geotechnical engineering related material, as an integral part of a civil engineering project, structure, or system. Geotextiles use fibers or yarns formed into a stable network. The structure of the geotextile reinforcements shall be dimensionally stable and be able to retain its geometry including selvages (edges), during shipping, handling, placement, and under construction stresses and have high resistance to damage during construction, to ultraviolet degradation, and to all forms of chemical and biological degradation encountered in the soil being reinforced. Geotextiles and the thread used in joining (seaming) geotextiles are manufactured from fibers consisting of long-chain polymers, composed of at least 95 percent by weight of polyolefins or polyesters. The geotextile shall be free from defects or tears. Supply only woven geotextiles unless otherwise indicated on the plans or in the Special Provisions. Geotextile design requirements and placement shall be as shown in the plans and shall meet the properties specified in Section 3.2. 3.2 Provide woven geotextiles meeting the following minimum allowable long-term reinforcement tension load, Tal or the tension load at 5 percent strain, T5 in the machine direction as indicated in the table below depending on the proposed application of the geotextile soil reinforcement. The proposed application of the geotextile soil reinforcement is indicated on the project plans, along with whether Tal or T5 is required. Tal is the Minimum Average Rolled Value (MARV) Tult that is reduced for construction installation damage, creep and durability. Similarly, T5 is the MARV at 5 percent strain. Obtain the following information from the grain- size testing of the proposed borrow materials and the subgrade if geotextile soil reinforcement will be placed directly on the subgrade: D10 = Diameter of particle at 10% finer material, millimeter (mm) D60 = Diameter of particle at 60% finer material, mm D85 = Diameter of particle at 85% finer material, mm 1 % No. 200 = Percent material passing the No. 200 Sieve, % Property GT1 GT2 GT3 GT4 GT5 GT6 GT7 GT8 GT9 GT10 Allowable Long-term Tension Load, T 1, 2, 3 or Tension al 450 800 1450 2300 3000 3600 4000 6000 9000 13000 Load at 5 Percent 1, 2, 3 Strain, T5 (lb/ft) C ≤ 2 or u B = 1.0 Cu ≥ 8 Apparent Opening 4,5 Size (AOS) 2 ≤ Cu ≤ 4 B = 0.5 * Cu AOS ≤ B * D85(soil) (mm) 4 ≤ Cu ≤ 8 B = 8 ÷ Cu Permeability k ≥ 10 * k (cm/s)6,7 geotextile soil % No. 200 < 15 ≥ 0.5 Permittivity 15 ≤ % No. 200 ≤ 50 ≥ 0.2 (sec-1)8 50 < % No. 200 ≥ 0.1 1. Based on the MARV Tult in machine direction (ASTM D4595) 2. Tal in cross machine direction at least 50% of MARV Tult in machine direction but no more than 3,000 pounds per foot (ASTM D4595) 3. Minimum pullout friction factor F*= 0.67*tan ϕ; based on ϕ ≥ 28° and Cu ≥ 4 (ASTM D6706) 4. AOS determined using ASTM D4751 5. AOS requirement does not apply to geotextiles made with polyester fibers 6. Permeability determined using ASTM D4491 (geotextile); use ASTM D5084 (soil % No. 200 ≥ 15) -3 7. Soils with less than 15% passing No. 200, assume ksoil = 1 * 10 cm/s 8. Permittivity determined using ASTM D4491 3.3 If sewn seams are shown in the plans, use thread that consists of either polypropylene or polyester polymers and which has a strength matching the strength of the geotextile being seamed. Do not use nylon thread. Use thread that is of contrasting color to that of the geotextile itself. Use a double row of double-thread chain stitch, Type 401 (see ASTM D6193). Use 150 to 400 stitches per yard depending on the weight of the geotextile. Consult the geotextile manufacturer or supplier for the appropriate stitch density. Use either a “butterfly” seam (Type SSd) or “J” seam (Type SSn) (see ASTM D6193). The sewn seam strength (whether field or factory sewn) shall meet the requirements indicated on the plans. 2 4.0 CERTIFICATION 4.1 Prior to construction, submit to the GEOR a Certification Package prepared by the geotextile reinforcement manufacturer. Allow 21 calendar days from the day the submittals are received by the GEOR for review and acceptance. State in the Certification Package that the furnished geotextile soil reinforcement is in full compliance with the design requirements as stated in this STS and the design drawings and is fit for use in long-term critical soil reinforcement applications. Certify and document the submittal values for the following items for each geotextile soil reinforcement used on the project: 1. The ultimate tensile strength, TULT, and percent strain at TULT for geotextile soil reinforcements 2. The allowable long-term tensile load, Tal, for geotextile soil reinforcements and the RFID, RFCR, and RFD used to determine Tal 3. The tensile strength at 5 percent strain, T5, for geotextile soil reinforcements 4. The geotextile’s pullout coefficients (F*, α) 4.2 Provide the written manufacturer’s certification that geotextiles manufactured from polypropylene (PP) or polyethylene (HPDE) are capable of withstanding direct exposure to sunlight for 500 hours with a minimum strength retained of 70 percent of Tult as measured per ASTM D4355. Provide the written manufacturer’s certification that geotextiles manufactured from polyester (PET) have a molecular weight greater than 25,000 (Mn > 25,000) (ASTM D4603 and GRI Test Method GG8) and a carboxyl end group less than 30 (CEG < 30) (ASTM D7409). Include in the submittal package, actual test results for tension, creep, durability, construction damage, seam strength, pullout, quality control and any other tests required by the Department. A person having the legal authority to bond the manufacturer shall attest to the certificate. If in the opinion of the GEOR, the required documentation is not provided for individual reduction factors (RF) or pullout coefficients (F*, α), use default values for these design parameters in accordance with this STS. 4.3 For products currently listed by the National Transportation Product Evaluation Program (NTPEP) Geosynthetic Reinforcement (REGEO) plan, base the submittal package on the posted independent product line evaluation report (see www.ntpep.org). For products that are not currently listed by the NTPEP, include in the submittal package all of the information required in the following Sections. 4.4 Certify in the submittal package the following values and document for each geotextile soil reinforcement used on the project: 4.4.1 The ultimate tensile strength, Tult, shall be determined from wide width tensile tests (ASTM D4595). Geotextile samples tested in accordance with ASTM D4595 shall be with an 8-inch width specimen, or a 4-inch specimen width with correlation to an 8-inch width. Correlation methodology shall be submitted to, and is subject to acceptance by the RCE and the GEOR. All geotextile strength tests (ASTM D4595) shall be conducted at a strain rate of 10% per minute based on actual gage length necessary to meet the testing sample dimension requirements. Laboratory test results documenting the ultimate tensile strength, Tult, in the reinforcement direction shall be based on the minimum average roll values (MARV) for the product. 4.4.2 Compute the allowable tensile load, Tal, per unit width of geotextile soil reinforcement for the specific backfill type used as follows: 3 4.4.3 The total reduction factor, RF, is the combined reduction factor for long-term degradation due to installation damage, creep, and durability. The total reduction factor, RF, is defined as follows: 4.4.4 Document the individual reduction factors in accordance with the site conditions, design calculations, and this STS. When sufficient documentation is not provided (i.e. the geotextile is not listed on the NTPEP website) for individual reduction factors, RFID, RFCR, and RFD, use a reduction factor RF of 7.0. Certify and document the individual reduction factors as follows: 4.4.4.1 Document the Reduction Factor for Installation Damage, RFID, using field and laboratory test results and literature review, as described in ASTM D5818 for the reinforced backfill specified or for more severe soils. Test samples subjected to installation damage for tensile strength and deformation characteristics in accordance with ASTM D4595. Document the recommended values for reduction factors for installation damage (RFID) for various soils. The installation damage reduction factor, RFID, shall be a minimum of 1.1, regardless of product specific test results. 4.4.4.2 Document the Reduction Factor for Creep, RFCR, using laboratory test results of creep performance over a range of load levels, for a minimum duration of 10,000 hours based on tension creep test (ASTM D5262).
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